1. Field of the Invention
This invention relates to workpiece holding apparatus and, more particularly, to an apparatus for holding a workpiece placed on a movable jig plate.
2. Description of the Prior Art
It is frequently necessary when mass producing a product to utilize automatic machinery to perform the work upon the item being manufactured. As part of such automatic machinery, it is frequently necessary to supply a means for holding the workpiece down while it is being moved about and having one or more production steps performed on it. Furthermore, since each workpiece is placed onto the automatic machine at the same initial place, the means for holding the workpiece down must also be capable of returning to that same initial starting point.
There exists in the prior art several means for holding the workpiece down and which return to the initial starting point. These means are usually operated by hydraulics, pneumatics, or electric motors. Since such holding means contain no memory in the structure itself, some other memory means must be provided in order to be able to return to the initial start position. Such memory means are usually complex and require such devices as cams, switches and in some cases a rudimentary tape-controlled computer.